Notes

Drought associated with earlier period in developing season reduces local community aboveground biomass, but boosts belowground biomass in the desert steppe.
ith F-PK. The GHGI in F-NPK+M and F-M treatments were significantly higher than that in other treatments. The GWP and GHGI in late rice season were 3091.6-6334.2 kg·hm-2 and 0.50-1.23 kg·kg-1, respectively. Irrigation significantly affected GWP and GHGI in both early and late rice seasons but fertilization had no significant impact on GWP and GHGI in late rice season. ④ Correlation analysis results showed that soil NH4+-N content and soil temperature below 5 cm soil layer had an extremely significant negative correlation with CH4 emissions. Soil pH was extremely significant positive correlated with CH4 emissions but significantly negatively correlated with N2O emission. Soil NH4+-N and NO3--N concentrations were extremely significantly negatively correlated with N2O emission. Given crop yield, GWP, GHGI, and D-NPK+M can be recommended for local water and fertilizer management to reduce greenhouse gas emissions while maintaining rice yields.Hydrochar can mitigate ammonia volatilization when applied in paddy fields due to its acidity and adsorption property. To realize the recycling of agricultural biowaste as well as the control of nutrient loss from paddy fields, a simulation soil-column experiment with wheat straw hydrochar (WHC) and water-washed hydrochar (W-WHC) was conducted to evaluate the performance of rice yield and ammonia volatilization from paddy fields. The results showed that WHC and W-WHC applied in paddy fields both increased the rice yield and the increased effect at low application rate (0.5%) was higher than that at high application rate (1.5%). In comparison with the control treatment (CKU), the rice yields achieved from low application rate treatments for WHC and W-WHC increased by 17.16% and 20.20% respectively. Except for the equal emission rate between W-WHC with low application rate and CKU treatments, hydrochar (WHC, W-WHC) addition reduced the ammonia volatilization from paddy fields when compared with the CKU. Among them, the ammonia volatilization levels from low-application WHC and high-application W-WHC treatments were significantly lower than that from the CKU treatment, reduced by 31.01% and 17.40%, respectively. Based on the analysis of ammonia volatilization during different fertilization stages, the control effect of hydrochar addition on ammonia volatilization was mainly benefited from tillering and panicle fertilizer stages. The change in the nitrogen concentration of surface water at the tillering fertilizer stage and in pH at the panicle fertilizer stage with the addition of hydrochar was the main driving factor for the reduction in ammonia volatilization. The results show that sufficient amounts of hydrochar derived from wheat straw application can increase crop yield while reducing ammonia volatilization from paddy fields. This method provides an effective route for recycling agricultural biowastes.Based on Landsat satellite remote sensing images, this study interprets land use changes in the Yangtze River Delta (YRD) region from 2000 to 2018. Combined with changes in nitrogen fertilizer application, the changes in ammonia emissions from farmland ecosystem due changes in land use and nitrogen fertilizer application were further investigated. The results show that along with the rapid urbanization process, the area of cultivated land in the YRD region has gradually decreased from 276269 km2 (49% of total land area) in 2000 to 244001 km2 (44%) in 2018. The effects of changes in land use and nitrogen fertilizer application on ammonia emissions from farmland ecosystems mainly include emissions from soil background and nitrogen fertilizer application. From 2000 to 2018, ammonia emissions due to the application of nitrogen fertilizer decreased from 690 kt·a-1 to 541 kt·a-1 (relative decrease by 22%), while the ammonia emissions from the soil background reduced from 32 kt·a-1 to 29 kt·a-1 (decrease by 9%). During the past 20 years, urbanization in the YRD region has accelerated, and the area of cultivated land and the total amount of nitrogen fertilizer application have significantly reduced, thus resulting in reductions in ammonia emissions from the farmland ecosystem.Taking urban domestic sludge as the research object, a slag-based modifying agent was used to modify sludge under different dosages and curing times, and the solidification effect of six heavy metals in the sludge, namely Zn, Cr, Cu, Pb, As, and Cd, were evaluated by analyzing stability efficiency and morphological changes. The results showed that the stability efficiency improved as curing time and dosage increased, reaching the maximum when the curing time was 14 d and the dosage was 50%. Under these conditions, Cu reached the maximum of 69.62%, and the most rapid growth was observed when dosages were 5%-20%. Through the regression analysis of adding amount, maintenance time and stability efficiency, it was found that the fitting correlation coefficient Cu was the highest 0.97, with a strong degree of fitting and a strong interaction between adding amount and maintenance time, which had a significant influence on the stability efficiency. In addition, Pb and As were the residual state, Cu and Cr were oxidizable state and residue state, Zn and Cd were reducible and extractable state as the main forms in the sludge after modifying, respectively. With the increase of curing time or dosage, the residual state of each heavy metal increased by 7%-86%. The results showed that the slag-based modifying agent could effectively solidify heavy metals in sludge and reused solid wastes such as sludge.Cold acclimation is an effective approach for improving the nitrogen removal performance and operational stability of partial nitritation/ANAMMOX (PN/A) combined processes at low temperatures. To explore the specific effects of cold acclimation on the characteristics of sludge, differentiations in temperature sensitivity, granular morphology, composition of extracellular polymer substance (EPS), and bacterial community structure between PN/A granular sludges cultivated at medium-high temperature (30℃) and acclimated to low temperature (15℃) were investigated in this study. The results of reaction thermodynamics showed that the nitrogen removal performance of the granules acclimated to low temperature (GL) was significantly higher than that of those cultivated at medium-high temperature (GH) under the low temperature (10-20℃), and the apparent activation energy (Ea) of total inorganic nitrogen removal for the former was decreased by 28.4%. Compared with GH, GL had a smaller average particle size of 25.8% and higher EPS contents of 16.6%, resulting in a significant lower settling property. Based on the high-throughput sequencing results, GL exhibited a higher diversity of bacterial community, and a lower relative abundance ratio (0.04) of aerobic ammonium-oxidizing bacteria (Nitrosomonas) and anaerobic ammonium-oxidizing bacteria (Candidatus_Kuenenia) than 0.34 for GH. It indicated that the PN/A granules held a strong ability to retain slow-growing autotrophic bacteria in the system, even under low temperatures. These findings could provide meaningful references for analyzing the self-adaption mechanisms of PN/A sludge to low temperature conditions and promote the industrial application of combined processes.In this study, three sequence batch reactors were selected to evaluate the effects of salt-tolerant activated sludge acclimation. The effect of salinity increase rate on pollutant removal, physicochemical characteristics of activated sludge, and microbial community were investigated. The results showed that a rapid salinity increase to 30‰ (within 30 d) reduced removal efficiencies of COD and NH4+-N from 85.5% and 98.5% (18 d) to 72.2% and 81.7% (51 d), respectively. ART558 In comparison, a slower salinity increases to 30‰ (within 90 d) had a minor effect on COD and NH4+-N removal. During the rapid salinity increase, a stable shortcut nitrification occurred under 20‰ salinity, in which the effluent NO2--N reached 11.13 mg·L-1 and NO3--N decreased to 0.56 mg·L-1. When salinity increased to 30‰, the nitrite accumulation rate was about 90%, and the removal efficiency of total nitrogen increased to approximately 75%. The contents of polysaccharide and protein in extracellular polymer substances increased as salinity increased, and the polysaccharide content increased significantly when the salinity was higher than 15‰. High-throughput sequencing results illustrated that microbial diversity reduced as salinity increased, following the Shannon index decrease from 8.06 (0‰ salinity) to 4.34 (rapid salinity increase) and 6.17 (slower salinity increase). As salinity increased, Micropruina, Denitromonas, TM7a, and Marinicella exhibited good salt tolerance. The relative abundance of Denitratisoma, Defluviimonas, Arenimonas, and Denitromonas decreased more significantly following the rapid salinity increase compared with that after the slower salinity increase.In this study, a SBR reactor was selected to explore the effect of nitrogen and phosphorus removal by aerobic granular sludge under different initial anaerobic time using intermittent gradient aeration (decreasing dissolved oxygen concentration in each aeration section) and actual domestic wastewater with low C/N ratio as the influent matrix. The results showed that the initial anaerobic stage of intermittent gradient aeration increased from 50 min to 90 min, which increased the carbon source reserves in granular sludge. This improved delayed anaerobic condition led to the improvement of nitrogen and phosphorus removal efficiency of granular sludge. When delayed to 70 and 90 min, the removal efficiency of COD, TN, and TP reached 84.74%, 70.05%, and 89.7% and 86.65%, 78.81%, and 85.5%, respectively. However, after the first anaerobic phase time was increased to 110 min, the sludge loss was more severe owing to the disintegration of some cells, leading to a decrease in internal carbon source reserves by about 13.6%. Owing to this, the pollutant removal efficiency decreased. In the process of prolonging the first anaerobic phase time from 50 min to 90 min, the content of PS in LB-EPS changed minimally; when it was delayed to 110 min, the content of PS increased to about 7.18 mg·g-1, and the PN content increased to about 5.56 mg·g-1. The contents of PN and PS in TB-EPS were stable, which indicated that the effect of internal carbon storage on LB-EPS was greater than that of TB-EPS, and the decrease in sludge settling performance was closely related to the increase in PS content in LB-EPS. The proportion of DPAOs in granular sludge increased as the first anaerobic phase time increased, and the proportion of DPAOs reached 51.5% when the first anaerobic phase time was 70 min.The effect of ozone dosage on sludge settleability and biological nutrient removal performance in a sequencing batch reactor was investigated by inoculating the bulking sludge with the SVI of 280 mL·g-1 from a wastewater treatment plant in winter. The filamentous mycelium was interrupted, and the SVI was decreased to 125 mL·g-1 after ozone dosage with a low concentration of 0.085 g·g-1(O3/MLSS) for 20 days, which indicated the disappearance of the sludge bulking. The performance of nitrification and phosphorus removal efficiency was not affected obviously. However, the sludge settleability deteriorated with a high dosage of ozone, and the phosphorus removal efficiency was decreased to around 60%. Further study showed that PS/PN had a positive correlation with SVI with the correlation coefficient of 0.9381, which can be used to characterize sludge settleability. A low ozone dosage not only interrupted the filamentous mycelium, but it also affected the content and composition of the EPS, which led to improved settleability.
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